1. Field of the Invention
The present invention relates to a recording unit having an ink jet head and applicable, for example, to a printer and a facsimile apparatus, and to an ink jet type recording apparatus using the same. In particular, the present invention relates to an ink jet head position adjusting mechanism.
2. Description of the Related Art
Conventionally, an ink jet type recording apparatus has been known which records characters and images on recording mediums by using an ink jet head ejecting ink from a plurality of nozzles. In this ink jet type recording apparatus, while moving a carriage on which the ink jet head is mounted in the main scanning direction with respect to the recording medium, ink is ejected from the nozzles of the ink jet head to print a dot pattern in a predetermined region. After the completion of one main scanning, the recording medium is moved in the sub scanning direction by a predetermined amount. By repeating these operations, printing is performed in the entire desired region.
In a large ink jet recording apparatus, a plurality of ink jet heads corresponding to inks of different colors are mounted on the carriage. In such a large ink jet recording apparatus, it is necessary to fasten the ink jet heads to the carriage while effecting positioning such that the nozzle interval in each ink jet head is adjusted with a relatively high level of accuracy to be within an error range, for example, of approximately xc2x135 xcexcm. When the positional accuracy of each ink jet type recording head is rather low, a printing deficiency, such as unevenness in density, occurs.
In view of this, in the conventional ink jet type recording apparatus, printing is executed, with the ink jet heads being temporarily installed, and in accordance with the positional deviation amount measured from the printing result, each ink jet head is moved through eye measurement. By repeatedly executing this operation, the position of each ink jet head is adjusted so as to be within a predetermined error range.
Here, generally speaking, the positional adjustment of an ink jet head consists of two adjustments: the adjustment of positional deviation in the sub scanning direction, and the adjustment of the angle with respect to the sub scanning direction. When, for example, the adjustment of positional deviation in the sub scanning direction is first conducted, and then the adjustment of the angle with respect to the sub scanning direction is conducted, the position in the sub scanning direction is deviated again. If the order of adjustment is altered, a similar angular deviation occurs, which means a fine positional adjustment of the ink jet head is difficult to perform.
To make this positional adjustment of the ink jet head relatively easy, a technique has been proposed according to which a wedge-like member, for example, is forced between the ink jet head and the carriage to thereby effect a fine positional adjustment.
According to another technique that has been proposed, a predetermined pattern is printed, and a positional deviation amount is automatically recognized from this printed pattern, the position of each ink jet head being automatically adjusted by a motor or the like.
In the former technique, however, while it is possible to move the ink jet head by a minute amount by forcing in the wedge-like member, it is rather difficult to accurately ascertain the movement amount. Further, once the ink jet head has been moved, it is difficult to restore it to the former position, with the result that the positional adjustment takes a lot of time.
In the latter case, positional adjustment can be conducted easily and reliably since the position of the ink jet head is automatically adjusted. However, this technique involves a complicated structure, resulting in a considerably high cost.
In view of the above problems, it is an object of the present invention to provide a recording unit and an ink jet recording apparatus in which it is possible to perform the head position adjustment easily and reliably with a relatively simple structure.
To solve the above-mentioned problem, according to a first aspect of the present invention, there is provided a recording unit comprising a plurality of ink jet heads having a plurality of nozzle openings for ejecting ink, and a carriage on which the plurality of ink jet heads are mounted, characterized in that: one end portions of the ink jet heads with respect to a sub scanning direction perpendicular to the scanning direction of the carriage are supported so as to be restricted in the movement of the scanning direction of the carriage with respect to the carriage and so as to be movable in the sub scanning direction and rotatable; and the other end portions of the ink jet heads are positioned and fastened to a slide member provided so as to allow positioning and movement in the sub scanning direction with respect to the carriage.
According to a second aspect of the present invention, in the first aspect of the invention, the recording unit is characterized in that the slide member is connected to the carriage by a screw member having a length covering at least the slide member and the carriage and adapted to be threadedly engaged with an associated female screw hole through a through-hole in one of the slide member and the carriage, and can be positioned and moved in the sub scanning direction by adjusting the amount by which the screw member is engaged with the female screw hole.
According to a third aspect of the present invention, in the first aspect of the invention, the recording unit is characterized in that: an engagement member fastened to the other end portions of the ink jet heads with respect to the sub scanning direction and the slide member are connected by a rotatably held eccentric pin, whereby the ink jet heads are positioned and fixed with respect to the carriage; and by rotating the eccentric pin, the other end portions of the ink jet heads can be moved in the scanning direction.
According to a fourth aspect of the present invention, in the second aspect of the invention, the recording unit is characterized by comprising a biasing member for biasing the ink jet heads in the sub scanning direction to fix them at positioning positions in correspondence with the amount by which the screw member is threadedly engaged.
According to a fifth aspect of the present invention, in the fourth aspect of the invention, the recording unit is characterized in that the biasing member is a spring member provided in the outer periphery of the screw member between the carriage and the slide member.
According to a sixth aspect of the present invention, in the third aspect of the invention, the recording unit is characterized in that the engagement member is formed integrally with the ink jet heads.
According to a seventh aspect of the present invention, in the first aspect of the invention, the recording unit is characterized in that a supply pipe for supplying ink to the ink jet heads is connected to the other ends of the ink jet heads with respect to the sub scanning direction.
According to an eighth aspect of the present invention, there is provided an ink jet type recording apparatus characterized in that it is equipped with a recording unit according to the first aspect.
In the present invention as described above, it is possible to perform the positional adjustment of the ink jet head with respect to the carriage easily and with high accuracy.